1. Field of Invention
The present invention relates to stage lighting equipment, and particularly to a motorized apparatus for directing a beam of light.
2. Discussion of the Prior Art
Motorized lighting instruments operable by remote control typically include a variety of mechanisms for adjusting the instrument's various parameters. For instance, such instruments may include a motor for adjusting azimuth (pan) and elevation (tilt). Lamp enclosure assemblies suspended between the arms of a yoke may include a motorized color changing mechanism and a motorized mechanism for altering beam dispersion properties. Instruments using an arc lamp as a source of light may employ a motorized mechanical dimmer.
Control of motorized lighting instruments typically is provided by an electronic control circuit located within the instrument itself. Such control circuits receive control signals, for instance, from a remotely located lighting system control console. In modern systems, these control signals may be digital signals generated in response to stored cue programs in the console or in response to manual adjustments to console controls. The control circuitry residing in the luminaire, therefore, in many cases is of the digital electronic variety. As is well known, such circuitry is extremely sensitive to heat.
Parameter change motors within motorized lighting instruments frequently receive power from an internal power supply. Likewise, a typical lighting instrument may include an internal power supply for lamp electronics, as well as for the lamp itself. Because of the enormous amount of heat generated by the lamp, the electronics and the position-changing motors, one or more fans usually are required to provide adequate cooling of electronic components.
In addition to the foregoing mechanical and electronic components, a typical lamp enclosure also houses the luminaire's entire optical system, including a lamp, a reflector, a color changing mechanism, a beam dispersion mechanism, and a mechanical dimmer. Depending upon the design of the lighting instrument, the lamp enclosure may also house a tilt mechanism.
One problem associated with housing electronics, parameter change motors, power supplies and optical components in a panning and tilting lamp enclosure arises from the excessive weight of the components. To initiate luminaire motion, therefore, the pan and tilt motors must overcome the inertia of the lamp enclosure, which inertia is directly related to the mass of the enclosure and its contents. Because of this large mass, a great deal of force is needed to move the enclosure. The mass of the enclosure similarly limits the speed of movement.
One approach to these problems is the use of larger and more powerful motors to overcome the inertia of the lamp enclosure. The benefit of such motors is marginal, however, because frequently one or more of such motors is housed in a movable portion of the lighting instrument, adding to the total weight to be moved and compounding the problem. In some systems, for instance, the tilt motor is housed in the rotating part of the instrument. Still other systems place both the pan and tilt motors within the movable yoke. In either case, however, placement of a motor in a movable component creates a need for larger motors than are necessary if the motor could be separated from the component to be moved.
several attempts have been made to overcome the compounding effect of placing larger motors in lighting instruments. One such attempt, as described in U.S. Pat. No. 5,089,946 to Mayer et al., utilizes a movable scanning mirror mounted along the beam path of a fixed lamp enclosure. The mirror has a reflective surface on only one side, the other side providing means for coupling the mirror to an X-Y deflection apparatus. The resulting lighting instrument is capable of high-speed beam steering, but with only a limited range of deflection.
Other attempts utilize two successive mirrors, each of which are rotated about separate axes, for azimuth and elevation adjustment. Instruments of this type are described in U.S. Pat. No. 4,663,698 to Tomlinson; U.S. Pat. Nos. 4,729,071 and 4,777,568 to Solomon; U.S. Pat. No. 4,843,529 to Izenour; and U.S. Pat. No. 4,827,387 to Ferren et al. Although there are differences among the lighting instruments described in these patents, the disclosed instruments are alike in that a light source directs a light beam toward a first mirror rotatable about a first axis, which mirror redirects the beam toward a second mirror rotatable about a second axis. The effect of such an instrument is to steer the beam in any direction without actually moving the lamp enclosure. One disadvantage of such instruments is that the use of two mirrors in succession doubles intensity losses typically experienced when a light beam is reflected from a reflective surface. Minimizing intensity losses in a dual-mirror beam-steering apparatus, therefore, requires the use of expensive, highly-reflective mirrors.
Another attempt to overcome the adverse effects of using larger motors is described in U.S. Pat. No. 4,769,743 to Callahan, which describes a system capable of high-speed beam direction about one axis. High speed beam direction is made possible by use of a low-inertia rotatable mirror mounted at one end of a tiltable lamp enclosure. The rotatable mirror provides beam direction in one coordinate, but the system still suffers from the problem arising from the excessive power needed to overcome the inertia of the lamp enclosure, which is rotatable to provide direction along another coordinate axis.
Another drawback to the above systems is that none is capable of "flipping" a light beam.
Accordingly, it is an object of the present invention to provide a variable light modifier which can direct a beam of Light quickly, accurately and precisely along more than one coordinate axis, while minimizing loss of beam intensity and the mass of the modifier's moveable components.